The present invention relates to a motor-vehicle door latch. More particularly this invention concerns such a latch having levers that, prior to finished installation, are movable relative to each other and that, after finished installation, are fixed relative to each other.
A standard motor-vehicle door latch has a latch housing mounted on a door edge, a latch fork pivotal on the housing and latchingly engageable around a doorpost-mounted lock bolt, and a lock pawl mounted on the housing for retaining the fork latched around the bolt or releasing it to free the bolt. This pawl can be moved into the fork-freeing position by inside and outside door handles, and the outside handle at least can be decoupled from the pawl by locking mechanisms inside and outside the door. Typically the outside handle is pulled out to open the door, as such movement makes pulling the door open a natural extension of the unlatching operation. To this end a lever linkage is provided that couples the outside door handle to the lock pawl.
Since manufacturing tolerances will inherently vary, it is standard as described in German patent document 4,005,369 of D. Sajfert, U.S. Pat. No. 5,071,179 of H. Brackmann, and U.S. Pat. 5,622,396 of F. Neumann to provide in the linkage between one of the door handles, typically the outside handle, and the pawl a pair of levers which pivot about the same axis and which can be coupled or decoupled. Prior to the finished installation the two levers are decoupled and normally urged together or apart by one or more springs so they can be set to fit exactly between the handle and the pawl or mechanism by which they are connected to the pawl. Once the installation of the handle and latch is complete, these levers are attached together fixedly so that henceforth they pivot jointly as a single element.
The two levers are usually coupled by a screw that has a thread engaged in or operatively coupled to one of the levers and a head that can bear against the other lever. This screw is offset from the common pivot for the two levers so that when it is tightened they are fixed together for joint pivoting. Normally the latch is delivered to the installer with the screw tightened and the two levers in their maximum spread position. After installation the screw is loosened to set the desired relative angular position, and then retightened to lock it in.
Since this unscrewing and screwing work is typically done in a mass-production operation by a power driver, either pneumatic or battery-operated, it is easy for the installer to back out the screw so much that it comes completely out of the part it is screwed in. The installer need merely leave his or her finger on the trigger of the power driver a split second too long, and the screw is free and has dropped out of position, making it necessary to take apart the latch and reassemble it, or scrap the latch.
It has been suggested to overcome this problem by making the screw relatively long so that its end extends past the threaded sleeve it is seated in. After a washer is slipped over this exposed end, this end is overturned like a rivet to prevent the washer from slipping off. Thus when backed out the screw will stop when the washer engages the back of the sleeve or nut it is screwed into. The obvious disadvantages of this system is that it adds an extra part to the latch, requires an extra assembly step, and puts the extra weight of the washer and extra-long screw in the latch.
It is therefore an object of the present invention to provide an improved motor-vehicle door latch.
Another object is the provision of such an improved motor-vehicle door latch which overcomes the above-given disadvantages, that is which has levers whose relative positions can be fixed by a simple screw that cannot be lost, but that is no more complex than the simplest prior-art system.
A motor-vehicle door latch has according to the invention a housing, a pair of levers pivoted at a common axis in the housing, a nut bearing axially on one of the levers and having a screwthread of a predetermined length, and a screw threaded in the nut, having a screwthread of a predetermined length, and having a head bearing axially oppositely on the other of the levers. Thus, when the screw is tightened in the nut, the two an levers are locked together for joint pivoting. An abutment in the housing axially spaced from and confronting the nut is spaced from the nut by a predetermined distance equal to less than each of the predetermined screwthread lengths.
The abutment therefore prevents the screw from being screwed completely out of the nut. Of course means such as a second abutment is provided to prevent the nut, which is formed as a sort of a T-nut with a threaded sleeve, from being pushed out of the one lever. With this system the nut and screw cannot be separated from each other while the housing is intact.
The two screwthread lengths in accordance with the invention are about equal to each other. In addition the nut is a sleeve formed with a groove adapted to hold a spring. This spring can also serve to prevent the nut from rotating in the housing.
The housing according to the invention is formed of two parts joined on a plane substantially perpendicular to the axis. The abutment is formed on one of the parts with a hole centered on the axis and the screw has a formation engageable through the hole by a tool for rotation of the screw. More particularly, the housing is formed with an inwardly projecting frustoconical collar forming the hold and the abutment. Thus the installer simply fits the tip of his screwdriver through the hole so as to rotate the screw. The screw has a head of substantially greater diameter than a diameter of the hole so it cannot be backed out through the hole.